Metal manufacturing systems and methods using mechanical oscillation

ABSTRACT

Present embodiments include a system that includes a welding tool configured to receive a welding wire from a wire feeder, to receive welding power from a power source, and to supply the welding wire to a workpiece during a welding process. The system also includes a mechanical oscillation system configured to mechanically oscillate a structural component toward and away from the workpiece. The structural component is external to the wire feeder and the power source. The system further comprises control circuitry configured to control the welding power based on feedback relating to the welding process.

BACKGROUND

The present disclosure relates generally to metal manufacturing systemsand methods and, more particularly, to systems and methods for joiningor building metal workpieces using mechanical oscillation of anelectrode.

Various manufactured products may incorporate components with differentmaterials. As may be appreciated, the different materials of themanufactured products may be joined together by fasteners, matinggeometries, welding, or other processes. Fasteners or complementarygeometries may add components or weight to the joint. Three dimensionalwelding and additive manufacturing with metals can be useful forcreating durable components in a controlled and precise manner.Unfortunately, such processes can be complicated and expensive.

BRIEF DESCRIPTION

In one embodiment, a system includes a welding tool configured toreceive a welding wire from a wire feeder, to receive welding power froma power source, and to supply the welding wire to a workpiece during awelding process. The system also includes a mechanical oscillationsystem configured to mechanically oscillate a structural componenttoward and away from the workpiece. The structural component is externalto the wire feeder and the power source.

In another embodiment, a system includes a welding tool configured toreceive a welding wire from a wire feeder, to receive welding power froma power source, and to supply the welding wire to a workpiece during awelding process. The system also includes a mechanical oscillationsystem configured to mechanically oscillate a structural componenttoward and away from the workpiece. The structural component is externalto the wire feeder and the power source. The system further comprisescontrol circuitry configured to control the welding power based onfeedback relating to the welding process.

In another embodiment, a system includes a welding tool configured toreceive a welding wire and to supply the welding wire to a workpiece.The welding tool comprises a mechanical oscillation system configured tomechanically oscillate a structural component of the welding tool towardand away from the workpiece. The system also includes control circuitryconfigured to receive an arc start command, to control the mechanicaloscillation system to start oscillation of the structural component, tocontrol a wire feeder to begin feeding the welding wire, to determinewhether an arc between the welding wire and the workpiece is initiatedbased at least in part on feedback received from a sensor, to controlthe mechanical oscillation system to stop oscillation of the structuralcomponent once the arc is determined to be established, and to controlthe wire feeder to increase a wire feed speed of the welding wire to adesired wire feed speed.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagram of an embodiment of a manufacturing system and apart;

FIG. 2 is a diagram of an embodiment of the manufacturing system and apart;

FIG. 3 is a diagram of an embodiment of the manufacturing system with anintegrated tool head;

FIG. 4 is a schematic of a mechanical oscillation system of themanufacturing system;

FIG. 5 is a graph illustrating a traveled distance of an electrode withrespect to time;

FIG. 6A is a schematic of a liner and an electrode of the manufacturingsystem;

FIG. 6B is a schematic of a liner and an electrode of the manufacturingsystem;

FIG. 7 is a perspective view of the mechanical oscillation system of themanufacturing system;

FIG. 8 illustrates time series of wire feed speed of a welding wireelectrode caused by the mechanical oscillation system, voltage ofelectrical power generated by a power source, and current of theelectrical power generated by the power source, in accordance with anexemplary controlled short circuit (CSS) wave shape implemented by acontroller;

FIG. 9 illustrates another set of time series of wire feed speed of thewelding wire electrode caused by the mechanical oscillation system,voltage of electrical power generated by the power source, and currentof the electrical power generated by the power source, in accordancewith another exemplary CSC wave shape implemented by the controller;

FIG. 10 illustrates another set of time series of wire feed speed of thewelding wire electrode caused by the mechanical oscillation system,voltage of electrical power generated by the power source, and currentof the electrical power generated by the power source, in accordancewith another exemplary CSC wave shape implemented by the controller; and

FIG. 11 is a flow chart that depicts an arc starting process that may beimplemented by the system.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

Turning to FIG. 1, an embodiment of a system 10 (e.g., an additivemanufacturing system or a welding system) that additively forms (e.g.,prints, builds) a part 12 from one or more anchoring materials 14. Theformed part 12 may be a first workpiece 16, a second workpiece 18, or ajoint between the first workpiece 16 and the second workpiece 18, or anycombination thereof. In some embodiments, the first and secondworkpieces 16, 18 may be of different materials having significantlydifferent physical properties. For example, in one embodiment, the firstworkpiece 16 may be aluminum and the second workpiece 18 may be steel.It is noted that FIGS. 1-3 primarily focus on embodiments where thesystem 10 is an additive manufacturing system configured to join theworkpieces 16, 18 to form the part 12, or to build the part 12 up fromone of the workpieces 16, 18, using multiple droplets 22 deposited ontothe workpieces 16, 18. However, as described in greater detail herein,in other embodiments, the system 10 may be a welding system configuredto join the workpieces 16, 18 by creating a welding arc between anelectrode 28 and the workpieces 16, 18 to form a weld between theworkpieces 16, 18.

In the embodiment illustrated in FIG. 1, a manufacturing tool 20deposits multiple droplets 22 to form (e.g., print, build) the part 12of the one or more anchoring materials 14. In some embodiments, themanufacturing tool 20 deposits the droplets 22 between the first andsecond workpieces 16, 18. As described in detail below, themanufacturing tool 20 may utilize one or more types of energy to formand deposit the droplets 22 to form the part 12. The one or more typesof energy utilized by the manufacturing tool 20 may include, but are notlimited to, an electric power output, photonic energy (e.g., laser), orany combination thereof. Where the part 12 is a joint between the firstand second workpieces 16, 18, the manufacturing tool 20 utilizes theenergy to join the first and second workpieces 16, 18 via the part 12.

The manufacturing tool 20 heats the one or more anchor materials 14 froma feeder 24 to form the droplets 22 having a desired composition. Insome embodiments, a mixer 26 of the manufacturing tool 20 is configuredto receive and to combine the one or more anchor materials 14 from thefeeder 24. For example, the mixer 26 may combine the multiple anchormaterials 14 into an electrode 28 having a desired combination of theanchor materials 14. In some embodiments, the mixer 26 may form a powdermixture of the multiple anchor materials 14. The electrode 28 and/or thepowder mixture may be formed into droplets 22. The one or more anchormaterials 14 are metallic materials that include, but are not limited,to aluminum alloys, steel alloys, aluminum, iron, copper, manganese,silicon, magnesium, zinc, chromium, titanium, molybdenum, and nickel. Asdiscussed herein, the droplets 22 are units of material transfer. Eachdroplet 22 may become a “micro-deposit” when solidified, and the part 12is formed from multiple micro-deposits 30.

FIG. 2 illustrates an embodiment of the manufacturing tool 20 thatdirects the anchor material 14 (e.g., electrode 28) into a molten puddle32 of micro-deposits 30 to form the part 12. The anchor material 14 maybe at approximately ambient temperature or a preheated temperature wheninserted into the puddle 32. A portion 34 (e.g., ball) of the anchormaterial 14 is melted by the puddle 32, thereby forming a micro-deposit30 of the part 12 without forming a defined droplet 22. For example, incertain embodiments, the preheated portion 34 of the anchor material 14may join the puddle 32, thereby forming the micro-deposit 30 of the part12 via a hotwire welding process. As may be appreciated, the puddle 32may be a recently formed section of the part 12 that has not yetsolidified. The energy applied to the puddle 32 that melts the portion34 may include, but is not limited, to resistance heating, photonic(laser) energy, plasma, or inductive heating.

Returning to FIG. 1, the one or more anchor materials 14 may include,but are not limited to, powders, solid wires, cored wires, tubularwires, or coated wires, or any combination thereof. In some embodiments,a first anchor material 36 may be substantially the material of thefirst workpiece 16, and a second anchor material 38 may be substantiallythe material of the second workpiece 18. In other words, the first andsecond anchor materials 36, 38 may have chemical compositions that aresubstantially similar or compatible to the respective first and secondworkpieces 16, 18. For example, the first anchor material 36 may haveonly minor differences (e.g., elemental components varying by onlyfractions of compositional percentages, different alloys from the samealloy family) relative to the material of the first workpiece 16. Insome embodiments, anchoring materials 14 may include, but are notlimited to, brazing or soldering materials with lower meltingtemperatures than the materials of the first workpiece 16 and/or thesecond workpiece 18. Anchor materials 14 with a lower meltingtemperature than the first or second workpieces 16, 18 may enable layersof micro-deposits 30 adjacent to the first or second materials 16, 18 tonot melt when the one or more anchoring materials 14 is applied. Someembodiments of the system 10 may include more than two anchoringmaterials 14, such as 3, 4, 5, 6, 7, 8, 9, 10, or more anchoringmaterials 14. For example, a third anchor material 40 may be supplied tothe manufacturing tool 20. The third anchor material 40 may have achemical composition that is substantially similar to the material ofthe first workpiece 16 or to the material of the second workpiece 18.Additionally, or in the alternative, the third anchor material 40 mayhave a chemical composition that is an alloying material that provides adesired property (e.g., adhesion, increased or decreased fluidity)between the first and second anchoring materials 36, 38, and/or thechemical composition of the third anchor material 40 may provide adesired property (e.g., strength, hardness, galvanic protection) to thepart 12.

A controller 42 of the system 10 controls the application of thedroplets 22 to form the part (e.g., anchor) 12 from the micro-deposits30. In certain embodiments, the controller 42 may be a single controlsystem with a single controller, or the controller 42 may includemultiple control systems or controllers. For example, multiple controlsystems of the controller 42 may be configured to regulate differentcomponents or systems of the system 10 and/or the multiple controlsystems may be responsive to a single, central controller of thecontroller 42. In some embodiments with wired anchor materials 14, thecontroller 42 controls the composition of the droplets 22 applied to thepart 12 by adjusting the relative quantities of the one or more anchormaterials 14 supplied to the mixer 26 of the manufacturing tool 20,which thereby forms the electrode 28. For example, where the firstanchor material 36 is substantially similar to or compatible with thematerial of the first workpiece 16, the controller 42 may increase therelative ratio of the first anchor material 36 in the electrode 28 toform (e.g., print) portions of the part 12 near the first workpiece 16.As discussed herein, the composition of each droplet 22 is based on theone or more anchor materials 14 that make up the respective droplet 22.The droplets 22 are liquid (e.g., molten) at least in part. In someembodiments, a droplet 22 may be a liquid anchor material 14encapsulating a solid element of the same or a different anchor material14. For example, the manufacturing tool 20 may at least partially meltonly an outer layer of a droplet 22.

In certain embodiments, the manufacturing tool 20 mixes (e.g., melts,sinters, compresses) multiple anchor materials 14 with the mixer 26 intoan electrode 28 with a mixed composition. The controller 42 may controlthe manufacturing tool 20 to form droplets 22 with the mixed compositionfrom the mixed electrode 28. The controller 42 may adjust thecomposition of the part (e.g., anchor) 12 by varying ratios of the oneor more anchor materials 14 in the mixed electrode 28. In someembodiments, the manufacturing tool 20 supplies each of the one or moreanchor materials 14 as a separate electrode 28 that the manufacturingtool 20 respectively forms into droplets 22. For example, the controller42 may control the manufacturing tool 20 to form separate droplets 22with different respective compositions from each of the multipleelectrodes 28. The controller 42 may adjust the composition of the part12 by varying ratios of the one or more anchor materials 14 applied asdroplets 22 to the part 12.

In some embodiments, the controller 42 is coupled to multiplemanufacturing tools 20, each supplying a separate anchor material 14 viaa respective electrode. The controller 42 may control each of themultiple manufacturing tools 20 to adjust the composition of the part 12by varying ratios of the anchor materials 14 supplied as droplets 22 byeach manufacturing tool 20. As illustrated in FIG. 3, in someembodiments, multiple feeders 24 may be combined in an integrated toolhead 44 of the manufacturing tool 20 to supply multiple anchor materials14 in rows or a grid. The integrated tool head 44 may increase thedeposition rate of the anchor materials 14 to form (e.g., print, buildup) the part 12. The integrated tool head 44 of the manufacturing tool20 may have multiple mixers 26 to receive and process the anchormaterials 14 into electrodes 28 and/or powder streams. The controller 42may control each mixer 26 so that each electrode 28 and/or powder streamhas the same composition. In some embodiments, the controller 42controls one or more mixers 26 so that the respective electrode 28 orpowder stream has a different composition than the electrode 28 orpowder stream from another mixer 26. The integrated tool head 44 mayenable the manufacturing tool 20 to form multiple layers 46 of the partat approximately the same time, thereby enabling a reduction ofproduction time for the part 12 by reducing a quantity of passes of themanufacturing tool 20 to form the part 12. A first layer 48 of the part12 formed of substantially solidified micro-deposits 30 is illustratedwith a grid 39. The micro-deposits 30 of a second layer 50 of the part12 formed between the first layer 48 and a third layer 52 may be hotterthan the micro-deposits 30 of the first layer 48, yet sufficientlysolidified to support and bond with the deposited droplets 22 of thethird layer 52. The controller 42 controls the deposition rate of thedroplets 22 and the rate of formation of the layers 46 by themanufacturing tool 20 to enable each layer to bond with the previouslyformed layer 46. For example, the controller 42 may decrease thedeposition rate or rate of layer formation as the manufacturing tool 20builds up the part 12.

Returning again to FIG. 1, the controller 42 controls a power source 54(e.g., a current-regulated power source) to adjust the power output(e.g., current output, voltage output, photonic energy) provided to themanufacturing tool 20 to melt the one or more anchor materials 14 intothe droplets 22. As may be appreciated, the power source 54 may include,but is not limited to, an engine-driven generator, a welding powersupply, an inverter, laser, an induction heater, or any combinationthereof. In embodiments where the power source 54 is a welding powersupply, the controller 42 may regulate operation (e.g., voltage leveland/or current level of output power) of the power source 54 based on astate of an operation, such as a welding operation. For example, thecontroller 42 may regulate operation of the power source 54 based on thewelding operation being in an arc state or a short state.

The controller 42 may control the power source 54 to provide a DC or ACpower output to the electrode 28 in a controlled waveform, similar to apulsed welding process or a short circuit welding process (e.g.,regulated metal deposition (RMD™)). In some embodiments, the controller42 controls the power source 54 and/or the feeder 24 to provide poweroutput to the electrode 28 via the manufacturing tool 20 to enable amodified short circuit welding process (e.g., controlled short circuit)to form the part 12. Additionally, the controller 42 facilitatesformation of the part 12 by controlling the manufacturing tool 20 toextend and retract the one or more electrodes 28 during a controlledshort circuit welding process. The power output provided to themanufacturing tool 20 melts the electrode 28 into the droplets 22, whichare deposited via the arc to the part 12 as micro-deposits 30. That is,in some embodiments, the electrode 28 is a welding wire, themanufacturing tool 20 is a welding torch (e.g., a welding tool)configured for a pulsed welding process or a short circuit weldingprocess, and the feeder 24 is a welding wire feeder. In suchembodiments, the welding torch 20 may layer micro-deposits 30 via thearc, thereby forming (e.g., building up, printing) the part 12 fromwelding wire 28 via a pulsed welding process and/or a short circuitwelding process (e.g., RMD™). As may be appreciated, some embodiments ofthe system 10 may include a gas supply 56 configured to provide one ormore shielding gases to the manufacturing tool 20. The one or moreshielding gases may include, but are not limited to, argon, carbondioxide, helium, nitrogen, hydrogen, and combinations thereof. Thesystem may be configured to include a flux delivery system configured toprovide one or more fluxes. These fluxes are of different compositionsto provide different end results, in particular, metallurgical results.

As described above, the controller 42 may control power output forprocesses utilizing electrical arc, and/or magnetic, and/or photonicenergy to heat the electrode 28. The controller 42 may control the rateat which the droplets 22 are applied to the part 12 by controlling thepower source 54. In some embodiments, the controller 42 controls aheating device 58 (e.g., inductor coil, resistive heater) to preheat theelectrode 28. Accordingly, the controller 42 may control the heatapplied to the electrode 28 to form the droplets 22. Additionally, or inthe alternative, the heating devices 58, 60, 62 may enable pre-heatingor post-heating of the electrode 28, the first workpiece 16, and/or thesecond workpiece 18 respectively. Preheating the electrode 28 may reducethe heat applied to the first and second workpieces 16, 18, therebyreducing the formation of a heat affected zone.

The droplets 22 added to the part 12 as micro-deposits 30 affect theheat added to the first workpiece 16 and the second workpiece 18. Theformation of the micro-deposits 30 may include, but is not limited to,heating the anchor material 14 (e.g., electrode 28) to form the droplet22, and cooling the micro-deposit 30 in the part 12. As may beappreciated, the heat of the droplet 22 and the cooling rate of themicro-deposit 30 may affect the microstructure of the micro-deposit 30formed by the respective droplet 22, thereby affecting the properties ofthe part 12. For example, the microstructure of the micro-deposits 30 ofthe part 12 at a first location 64 may be different than themicrostructure of the micro-deposits 30 at a second location 66.Additionally, as discussed herein, the application of each droplet 22 tothe part 12 may include, but is not limited to, the application rate ofdroplets 22 to the part 12 and the application location on the part 12of each micro-deposit 30. The controller 42 may control the temperatureof the droplets 22, the application (e.g., deposition) rate, and theapplication location of each droplet 22 to control the heat applied tothe workpieces 16, 18. For example, the controller 42 may reduce theinducement of a heat affected zone (HAZ) that may affect themicrostructure and properties (e.g., strength, fatigue life) of theworkpieces 16, 18 proximate to the part 12. The temperature, depositionrate, and application location of the droplets 22 in the part 12 affectsthe heat added to the first workpiece 16 and the second workpiece 18.For example, an arc at 2000° C. adds more heat to the part 12 than anarc at 1200° C. As may be appreciated, high deposition rates (e.g., 60Hz) of droplets 22 may add less heat to the part 12 than relativelylower deposition rates (e.g., 30 Hz) of droplets 22. Additionally,droplets 22 applied at the first location 64 on the first workpiece 16add more heat to the first workpiece 16 than droplets 22 applied at thesecond location 66 on the first workpiece 16. In some embodiments, thecontroller 42 controls the heating device 58 to affect the applicationtemperature of the micro-deposits 30 in the part 12 to affect the heatadded to the first workpiece 16 and the second workpiece 18. Thecontroller 42 may control the feeder 24 and/or the mixer 26 to controlthe application rate, and the controller 42 may control the power source54 to control the application rate and the application temperature ofthe droplets 22 as the micro-deposits in the part 12. In someembodiments, a robotic system 68 coupled to the manufacturing tool 20may including control circuitry configured to control the applicationlocation of the droplets 22 by moving the manufacturing tool 20 alongcoordinate axes 70 via one or more servomotors 69.

In a similar manner to controlling the heat applied to the workpieces16, 18, the controller 42 may control the temperature of the droplets22, the application rate of the droplets 22, and the applicationlocation of each droplet 22 to control the heat applied to previouslyapplied micro-deposits 30. For example, the application rate and thetemperature of the droplets 22 may affect the cooling rate andmicrostructure of previously applied micro-deposits 30. The controller42 may control the application rate and the temperature of the droplets22 to achieve a desired microstructure for each of the micro-deposits 30utilized to form the part 12. Accordingly, the controller may controlthe composition and/or the microstructure of the micro-deposits 30 ofthe part 12.

In some embodiments, a first heating device 60 may heat the firstworkpiece 16 near the part 12, and/or a second heating device 62 mayheat the second workpiece 18 near the part 12 (e.g., joint). The firstand second heating devices 60, 62 may include, but are not limited to,induction coils, resistance heaters, flames, and so forth. The first andsecond heating devices 60, 62 may interface with one or more surfaces ofthe respective first and second workpieces 16, 18. For example, thefirst heating device 60 may extend around the first workpiece 16. Thecontroller 42 may control the first heating device 60 and/or the secondheating device 62 to preheat the respective workpieces 16, 18 near thepart 12. As may be appreciated, preheating a workpiece 16, 18 may affectthe adhesion to micro-deposits 30 from the tool 20. For example,increasing the temperature of the first workpiece 16 may increase theadhesion of the micro-deposits 30 at the first location 64. In someembodiments, the controller 42 independently controls the first andsecond heating devices 60, 62, thereby enabling the first workpiece 16to be preheated to a different temperature than the second workpiece 18.

As discussed previously, the first workpiece 16 may be different fromthe second workpiece 18. For example, the first workpiece 16 may bealuminum and the second workpiece 18 may be steel. In some embodiments,the first and second workpieces 16, 18 may be the same or differentcompositions with the same base metal (e.g., aluminum, titanium, iron,galvanized-coated material, high strength steel). For example, the firstworkpiece 16 may be a nickel coated steel, and the second workpiece 18may be a relatively high-carbon steel. The first workpiece 16 may havedifferent properties and/or structure than the second workpiece 18. Forexample, the melting temperature, thermal conductivity, and strength,among other properties, may differ between the first workpiece 16 andthe second workpiece 18. Additionally, or in the alternative, the firstworkpiece 16 and the second workpiece 18 may have differentsensitivities to heat. For example, the first workpiece 16 may beannealed at a melting temperature of the second workpiece 18.Accordingly, annealing the first workpiece 16 (e.g., by heating it tothe melting temperature of the second workpiece 18) may affectproperties (e.g., strength, fatigue-life) of the first workpiece 16.

As may be appreciated, the heat affected zone (HAZ) of a metal may bedefined herein as the area of the metal in which the properties and/ormicrostructure of the metal has been affected by heat. In someembodiments, the controller 42 may independently control the heatapplied to the electrode 28, the heat applied to the first workpiece 16(e.g., via the first heating device 60), and the heat applied to thesecond workpiece 18 (e.g., via the second heating device 62). Throughindependent control of the heat applied to these components, the system10 may reduce the HAZ of the first workpiece 16 and/or the secondworkpiece 18. For example, if the first workpiece 16 is aluminum and thesecond workpiece 18 is a steel with a higher melting temperature thanthe first workpiece 16, the controller 42 may control the manufacturingtool 20 to apply the droplets 22 near the second workpiece 18 (e.g.,steel) with more heat and/or at a higher rate than the droplets 22 nearthe first workpiece 16 (e.g., aluminum).

The controller 42 may control the composition and the formation of eachof the droplets 22 applied to build the part 12 with micro-deposits 30as the manufacturing tool 20 moves between the first workpiece 16 andthe second workpiece 18. In this way, the system 10 may control thecomposition and structure (e.g., spatial distribution of themicro-deposits 30) of the part 12 to have a desired set of propertieswhile controlling the HAZ of the first and/or second workpieces 16, 18.

One or more sensors 72 may be used to detect certain operatingparameters of the system 10. Although illustrated as being part of thewelding tool 20, in other embodiments, the sensors 72 may be part of anyother components of the system 10, including the feeder 24, the powersource 54, the gas supply 56, the robotic system 68, or any combinationthereof. In certain embodiments, the controller 42 may use the detectedoperating parameters as feedback to control various operating parametersof the system 10. For example, in certain embodiments, the sensors 72(e.g., temperature sensors) may measure the temperature and cooling rateof the electrode 28, the first workpiece 16, and/or the second workpiece18. Feedback from the sensors 72 may be stored as temperature history ofthe electrode 28, the first workpiece 16, and/or the second workpiece18. The controller 42 may use this temperature history to control thecomposition and structure of the part 12. In some embodiments, thesensors 72 (e.g., optical sensors, proximity sensors, and so forth) maymeasure the position of the manufacturing tool 20, first workpiece 16,and second workpiece 18 relative to the set of coordinate axes 70. Thecontroller 42 may control the application of the droplets 22 to the part12 based at least in part on the relative distance from the firstworkpiece 16 and/or the second workpiece 18. For example, in someapplications, the part 12 may be formed to have a gradient compositionof the first and second anchor materials 36, 38, such that thecomposition of the part 12 adjacent to the first workpiece 16 iscompatible (e.g., forming a strong bond) with the first workpiece 16,and the composition of the part 12 adjacent to the second workpiece 18is compatible (e.g., forming a strong bond) with the second workpiece18.

The controller 42 may independently control the thermal cycle, peaktemperature, and cooling rates of each of the micro-deposits 30 based atleast in part on the application location in the part 12. The controller42 may independently control the composition and the formation of eachof the droplets 22 for the application location according to a set ofinstructions (e.g., code) executed by a processor 74. The processor 74may load the set of instructions from a memory 76 based at least in parton the workpieces 16, 18 and the anchor materials 14. In someembodiments, an operator (e.g., from a host computer) may provide theset of instructions directly to the controller 42 via an operatorinterface 78. For example, the operator may load a set of instructionsfor forming the part 12 from a three-dimensional model (e.g., computeraided design (CAD) model) of the anchor produced by a three-dimensional3D CAD tool. In some embodiments, the controller 42 may receive and/orproduce a set of instructions to produce the part 12 with a desiredcomposition of anchor materials 14. For example, the controller 42 mayutilize a 3D CAD model of the part 12 to control the robotic system 68to produce the part 12 from the anchor materials 14. Although describedherein as controlling the robotic system 68, in other embodiments, thecontroller 42 may not be used to control the robotic system 68. Rather,in such embodiments, separate control circuitry of the robotic system 68may control the robotic system 68, for example, to control mechanicaloscillation of the welding tool 20. Alternatively, in certainembodiments, the controller 42 may operate in conjunction with controlcircuitry of the robotic system 68. Additionally, or in the alternative,an operator may input information about the workpieces 16, 18 and theanchor materials 14 into the operator interface 78, and the controller42 may determine and/or modify the set of instructions to form the part12 with desired characteristics. The set of instructions directs thecontroller 42 to control the composition, formation, and application ofeach droplet 22 as a micro-deposit 30 to form the part 12 with desiredcharacteristics.

The controller 42 may use input from the sensors 72 to individuallycontrol each droplet 22 applied to the part 12 as a micro-deposit 30. Insome embodiments, the controller 42 may adapt the set of instructionsbased at least in part on the input from the sensors 72 to compensatefor changes to the first workpiece 16, the second workpiece 18, or thepart 12. For example, the controller 42 may adapt the applicationlocation and/or the heating of the droplets 22 during the formation ofthe part 12 if the input from the sensors 72 indicates a change in thefit-up of a joint between the first workpiece 16 and the secondworkpiece 18. Additionally, or in the alternative, the controller 42 mayadapt the application and/or the heating of the droplets if the inputfrom the sensors 72 indicate a deflection or burn through of the firstworkpiece 16 and/or the second workpiece 18 and/or the previous layer.The controller 42 may adapt the temperature of the first workpiece 16and/or the temperature of the second workpiece 18 (e.g., via the heatingdevices 60, 62) during the formation of the part 12 if the input fromthe sensors 72 indicates a deflection or burn through of the firstworkpiece 16 and/or the second workpiece 18 and/or the previous layer.

The system 10 may build the part 12 between the first workpiece 16 andthe second workpiece 18 by manual or automatic movement of themanufacturing tool 20. In some embodiments, the droplets 22 may bedeposited via the arc (e.g. spray) as shown in FIG. 1. In someembodiments as illustrated in FIG. 2, the electrode 28 contacts theworkpiece and/or part 12, and the manufacturing tool 20 applies therespective micro-deposits 30 via short circuit. In some embodiments, anoperator begins or resumes building the part 12 by actuating a trigger80 on the manufacturing tool 20. The controller 42 determines a locationof the manufacturing tool 20 relative to the workpieces 16, 18 via thesensors 72, and the controller 42 determines the application location ofthe micro-deposits 30 prior to formation of the droplets 22 of thedesired composition according to the set of instructions. In someembodiments, the robotic system 68 controls the movement of themanufacturing tool 20 along the coordinate axes 70, such as viaservomotors 69. The controller 42 may control the robotic system 68 withthe set of instructions to move the manufacturing tool 20 to apply thecontrolled droplets 22 as micro-deposits 30 to respective locations inthe part 12 based on the set of instructions. The robotic system 68thereby enables the controller 42 to automatically form parts 12 with adesired composition and geometry. In some embodiments, the roboticsystem 68 may form (e.g., print, build up) the parts 12 from the one ormore anchor materials 14 separate from the workpieces 16, 18. The formedparts 12 may later be joined with the workpieces 16, 18.

Again, as described above, although the description of FIGS. 1-3 hasbeen primarily focused on additive manufacturing techniques (i.e., wherethe manufacturing tool 20 is an additive manufacturing tool), in otherembodiments, the system 10 may instead be a welding system 10 whereinthe manufacturing tool 20 is a welding torch configured to feed awelding wire (e.g., the electrode 28) from a welding wire feeder (e.g.,the feeder 24). As such, in such embodiments, instead of includingcomponents for supplying one or more anchor materials 14, the feeder 24may instead be a welding wire feeder including components (e.g., awelding wire spool, welding wire drive assembly, and so forth) forfeeding a welding wire electrode 28 from the feeder 24. In addition, insuch embodiments, the manufacturing tool 20 may be a welding torchconfigured to feed the welding wire electrode 28 received from thewelding wire feeder 24 toward the workpieces 16, 18 to establish awelding arc with one or more of the workpieces 16, 18.

In certain embodiments, the manufacturing tool 20 may be a handheldtool, such as a handheld welding torch (e.g., manipulatable by a humanoperator), whereas in other embodiments, the manufacturing tool 20 maybe used in fully automated or semi-automated processes (i.e., eitherfully controlled or partially controlled by a robotic system, such asthe robotic system 68 described herein). In any event, the manufacturingtool 20 described herein is external to (i.e., separate from) the feeder24 and the power source 54 described herein.

Regardless of whether the system 10 is an additive manufacturing systemor a welding system, in certain embodiments, the integrated tool head 44of the manufacturing tool 20 may be configured to mechanically oscillate(i.e., move up and down away and towards the puddle 32) to furtherimprove deposition of the droplets 22 onto the part 12. In other words,the integrated tool head 44, through which the electrode 28 and a liner100 disposed about the electrode 28 extend, may be oscillated to movethe electrode 28 and the liner 100 towards and away from the puddle 32.In FIG. 4, a mechanical oscillation system 102 is shown coupled to theintegrated tool head 44. The mechanical oscillation system 102 includesa mechanical linkage assembly coupled to the integrated tool head 44. Inthe illustrated embodiment, the mechanical linkage assembly includes apiston 104 coupled or fixedly attached to the integrated tool head 44(e.g., via a pin 106), a cam 108 coupled to the piston 104, and a motor110 configured to drive rotation of the cam 108. In other embodiments,the mechanical linkage assembly and/or the mechanical oscillation system100 may be directly coupled to the liner 100 to oscillate the liner 100toward and away from a workpiece. In operation, the mechanicaloscillation system 102 periodically shortens or lengthens the path thatthe electrode 28 must travel to the puddle 32 by moving the liner 100toward and away from the puddle 32 (e.g., a workpiece). In this manner,the mechanical oscillation system 102 may be used to break or remove theelectrode 28 from the puddle 32 to help form the droplets 22 in acontrolled manner. The mechanical oscillation system 102 also may beoperated to regulate or control a state of a welding operation. Forexample, the mechanical oscillation system 102 may operate to enable orimprove switching of the welding operation between an arc state and ashort state.

In certain embodiments, the mechanical oscillation system 102 may bedisposed within the tool 20 (e.g., within a housing of the welding tool20). In other embodiments, the mechanical oscillation system 102 may bedisposed external to the tool 20. For example, in such embodiments, themechanical oscillation system 102 may be at least partially integratedwith the robotic system 68 described herein. In any event, in certainembodiments, the mechanical oscillation system 102 is disposed externalto (e.g., outside of a housing of) the feeder 24 and the power source 54described herein. It will be appreciated that the integrated tool head44 and the liner 100 are at least partially disposed within the tool 20,and external to (e.g., outside of a housing of) the feeder 24 and thepower source 54 described herein, during operation.

As discussed in detail below, the manufacturing tool 20 with themechanical oscillation system 102 disclosed herein may be operated atsubstantially fixed frequencies and/or with a limited (e.g.,substantially fixed) travel distance of the integrated tool head 44. Asa result, the simplicity of the process may be increased, whilesignificantly reducing costs of the manufacturing tool 20 and themechanical oscillation system 102. For example, the disclosed mechanicaloscillation system 102 enables the formation of the droplets 22 at a lowwelding current. As will be appreciated, in other embodiments, themechanical oscillation system 102 may have other components. Forexample, instead of the motor 110, piston 104, and cam 106, themechanical oscillation system 102 may be an electro-magnetic system thatincludes coils, magnets, other mechanical linkage assemblies, and soforth, to enable an oscillating motion of the integrated tool head 44,or other structural component, and therefore the liner 100 coupled tothe integrated tool head 44. In certain embodiments, the mechanicaloscillation system 102 may directly interact with the liner 100 toenable oscillating motion of the liner 100. In other words, thestructural component that is mechanically oscillated by the mechanicaloscillation system 102 may be the liner 100 (i.e., instead of theintegrated tool head 44 indirectly causing the mechanical oscillation ofthe liner 100).

As mentioned above, the illustrated mechanical oscillation system 102(e.g., mechanical linkage assembly) includes the piston 104 coupled orfixedly attached to the integrated tool head 44, the cam 108 coupled tothe piston 104, and the motor 110 configured to drive rotation of thecam 108. In certain embodiments, the operation of the motor 110 may becontrolled and/or regulated by the controller 42. As the motor 110drives rotation of the cam 108, the rotation of the cam 108 will actuatethe piston 104 up and down, as indicated by arrows 112. Thus, theintegrated tool head 44, which may include a bushing, collar, gasnozzle, contact tip, a gas diffuser, an inlet wire guide, or othercomponent fixed to the piston 104, also travels up and down. In thismanner, the liner 100 and the electrode 28 are moved towards and awayfrom the puddle 32. As will be appreciated, the travel distance of theintegrated tool head 44 may be selected based on a size and/or geometryof the cam 108.

When the integrated tool head 44 oscillates upward, the liner 100 andthe electrode 28 are pulled away from the puddle 32, and as theintegrated tool head 44 oscillates downward, the liner 100 and theelectrode 28 are moved downward toward the puddle 32. Of course, whilethe mechanical oscillation system 102 is operating and moving theintegrated tool head 44 up and down, the electrode 28 is continuouslybeing fed downward toward the puddle 32. Thus, the electrode 28 may havean overall travel distance, which is represented by line 120 in thegraph 122 of FIG. 5. As will be appreciated, a peak to peak amplitude124 of the line 120 may represent the travel distance of the mechanicaloscillation system 102 (e.g., the piston 104 and the integrated toolhead 44). The gradual increase in overall travel distance of the line120 may be attributed to the constant feeding of the electrode 28 by thefeeder 24.

As mentioned above, the liner 100 is disposed about the electrode 28,and the liner 100 is held and supported by the integrated tool head 44.Thus, when the mechanical oscillation system 102 oscillates theintegrated tool head 44, the integrated tool head 44 similarlyoscillates the liner 100 directly, but may not directly oscillate theelectrode 28. To help facilitate oscillation of the electrode 28 aswell, the size of liner 100 may be selected to enable oscillation of theelectrode 28 as well.

Oscillation of the liner 100 and the electrode 28 is shown schematicallyin FIGS. 6A and 6B. The integrated tool head 44 and the mechanicaloscillation system 102 are not shown. In FIG. 6A, the liner 100 andelectrode 28 have not been oscillated upwards by the integrated toolhead 44 and the mechanical oscillation system 102. In other words, inFIG. 6A, the liner 100 and electrode 28 are extended fully downwardtowards the puddle 32. However, in FIG. 6B, the liner 100 and electrode28 are shown as retracted from the puddle 32 due to oscillation of themechanical oscillation system 102. In particular, the liner 100 andelectrode 28 are retracted the distance 124 (i.e., the peak to peakamplitude shown in FIG. 5). As will be appreciated, a space or gap 130may exist between the liner 100 and electrode 28, as the liner 100 is atube or sheath disposed about the electrode 28. This gap 130 may beconsidered when selecting the size of the cam 108 and/or the sizes andgeometries of other components of the mechanical oscillation system 102.Specifically, as the liner 100 is directly retracted by the integratedtool head 44 and the mechanical oscillation system 102, the liner 100may initially retract without similar retraction of electrode 28 due tothe gap 130 between the liner 100 and the electrode 28. Once the liner100 is directly retracted an initial amount, the liner 100 and theelectrode 28 may contact one another and frictionally engage, therebyenabling the retraction of the electrode 28 as well. To ensure theelectrode 28 retracts a desired amount (i.e., distance 124), the initialretraction of the liner 100 and the gap 130 between the liner 100 andthe electrode 28 may be considered when selecting the sizes andgeometries of the components of the mechanical oscillation system 102,such as the cam 108. In certain embodiments, the gap 130 between theliner 100 and electrode 28 may be minimized to improve consistency andaccuracy of the oscillating movement of the liner 100 and electrode 28.

The somewhat fixed frequency and fixed distance operation of themechanical oscillation system 102 enables increased simplicity andgreatly reduced cost of the manufacturing tool 20, and thus may not begreatly customizable. However, customization and modification of theoperation of the manufacturing tool 20 may be enabled by adjusting,regulating, or otherwise controlling electrical power of themanufacturing tool 20. In certain embodiments, the power source 54 maybe controlled such that a constant current is applied to the electrode28. In particular, if the distance 124 that the mechanical oscillationsystem 102 retracts the electrode 28 from the puddle 32 is sufficientlygreat, the welding current may remain at a fixed level. The fixedcurrent level may be relatively low, but great enough to melt theelectrode 28 and form one droplet 22 at a time. The low constant currentmay also not cause agitation of the puddle 32.

However, in other embodiments, one or more simple dynamic changes may beapplied to the welding current. For example, the controller 42 mayregulate operation of the power source 54 to adjust different dynamicsof the welding current. For example, dynamic wave shaping may be used,but the changes may be relatively minor to maintain simplicity and lowcosts. For example, when the liner 100 and electrode 28 are retracted bythe mechanical oscillation system 102, and after an arc is initiated atlow current, the current supplied by the power source 54 may beincreased by the controller 42. Increasing the current at this time mayhelp form the next droplet 22, help reduce the possibility of puddle 32oscillations reattaching to the electrode 28, and/or increase the amountof electrode 28 that can be deposited with the next droplet 22.

As the mechanical oscillation system 102 oscillates the liner 100 andelectrode 28 back toward the puddle 32, the current may be reduced(e.g., by the controller 42) as the electrode 28 nears the puddle 32.Reducing the current may help reduce the possibility of the electrode 28burning away as the electrode 28 tries to contact the puddle 32 and/orreduce the possibility of the electrode 28 and the next droplet 22contacting the puddle 32 and being “rejected” by the puddle 32. In otherembodiments, the current may be maintained at a level substantiallylower (e.g., at least 10, 20, 30, 40, 50, 60, 70, or 80 percent lower)than a peak current level (e.g., below 100 amps, below 75 amps, below 50amps, below 25 amps, between 10-100 amps, between 10-75 amps, between10-50 amps, between 10-25 amps, and so forth) of the system 10 as theliner 100 and electrode 28 are oscillated toward and/or away from thepuddle 32. In general, the substantially lower current level may bebelow 100 amps to avoid spatter, but above 10 amps to avoid the arcgoing out.

After the next droplet 22 is formed during the arc, and as themechanical oscillation system 102 is about to oscillate toward thepuddle 32 again, the current may remain reduced or be reduced further tofurther reduce puddle 32 agitation. Holding the current low (e.g.,substantially lower than a peak current level, as previously described)as the mechanical oscillation system 102 (and the liner 100 andelectrode 28) oscillate back away from the puddle 32 also helps leavethe newly formed droplet 22 in the puddle 32. More specifically, thecurrent may be held low during a short, and after the short clears, thecurrent may briefly increased to form the droplet 22. The current mayalso be held low, as discussed above, immediately prior to a statechange of a welding operation (e.g., immediately prior to a short or anarc). In certain embodiments, this may be accompanied by a constantvoltage. After the droplet 22 is formed, the current is then lowered toreduce agitation of the puddle 32 as the electrode 28 is oscillated awayfrom the puddle 32 again by the mechanical oscillation system 102.

To synchronize operation of the mechanical oscillation system 102 andthe power source 54 to achieve the operation described above, thesensors 72 may include position sensors or other types of sensors thatdetect a location of the integrated tool head 44 at a particular time.For example, the sensors 72 may detect a position of the integrated toolhead 44, the piston 106, the cam 108, the liner 100, the electrode 28,or other component. Based on the one or more detected positions, thecontroller 42 may regulate operation of the power source 54 such thatthe current output of the power source 54 is a desired level for aparticular position of the electrode 28. Other types of sensors 72 mayalso be used to detect other operating parameters, which may be used toalso synchronize operation of the mechanical oscillation system 102 andthe power source 54. For example, one or more of the sensors 72 mayinclude voltage-sensing circuitry and/or current-sensing circuitry,which may be used to detect voltage and/or current of the power source54 and/or the motor 110 (e.g., and therefore detect a state of a weldingoperation, such as a short or an arc). Other operating parameters may bedetected by the sensors 72, such as a phase of operation of themechanical oscillation system 102, the power source 54, and/or the motor110, welding arc presence, a short circuit (short circuits per second),angular velocity of the motor 110, load on the motor 110, wire feedspeed, arc length, a clearing event, a shorting event, an arc event, astate change, or other operating parameter of the system 10.

FIG. 7 is a perspective view of an embodiment of the mechanicaloscillation system 102, illustrating the mechanical linkage assemblyhaving the piston 104, the cam 108, and the motor 110. As discussedabove, the liner 100 may be secured to the piston 104 via the pin 106 orother coupling feature. As the motor 110 drives rotation of the cam 108,the piston 104 is actuated up and down in an oscillating manner, therebyoscillating the liner 100 and electrode 28 up and down. Thus, theelectrode 28 is moved toward and away from the puddle 32. In thismanner, the mechanical oscillation system 102 enables a simple and costeffective method of operating the manufacturing tool 20.

In another embodiment, a contact tip is moved along with the liner 100.In this case, the contact tip has higher friction then the liner andfacilitates tighter control. In addition, this motion also inherentlychanges the distance from the point of current conduction in the contacttip to the weld. Whereas when the contact tip is in a largely fixedlocation, the distance between the point of current conduction in thecontact tip to the weld is nearly constant. In either case, the keyeffect of retracting the wire from the molten weld is accomplished.Similarly, in other embodiments, the liner 100 may be moved along with agas nozzle, collar, bushing, or other structural component surroundingor coupled to the liner 100.

The embodiments described herein generally require that the droplets 22be deposited in a very controlled manner. One method is to use a weldingprocess that is very controlled, such as tungsten inert gas (TIG)applications and low-heat input metal inert gas (MIG) applications. Whenclosely controlled, most welding processes under ideal conditions canreplicate additive manufacturing processes. The most controlled weldingprocesses include Accu-Pulse™, RMD™, and controlled short circuit (CSC)welding process. The RMD™ and CSC processes are short circuit weldingprocesses. Theses short circuit welding processes are relativelyeffective for additive manufacturing because they involve relatively lowheat. By comparison, spray and pulsed spray welding processes arerelatively hotter, and therefore create a more fluid puddle, which isnot as effective for precise buildup (e.g., the puddle and resultantweld bead would tend to get too wide).

CSC processes, which are described in more detail in U.S. Pat. Nos.6,963,048, 6,969,823, and 6,984,806, each of which is herebyincorporated by reference in their entireties, use both electrical powermodulations as well as forward/reverse movement of welding wire tomaximize metal deposition. In general, in CSC processes, a short circuitstate is entered by advancing the wire until the wire touches the weldpool, and then an arc state is entered by retracting the wire until thewire does not touch the weld pool, at which point an arc forms. CSCprocesses typically employ sophisticated power output control techniquesto control the energy delivered to the weld. By separating the controlof the transitions between the states from the control of energydelivered to the weld, CSC processes allow for better control of each.

In general, a CSC system requires the capability of advancing andretracting the wire. Conventional CSC systems utilize certain mechanicalmeans, such as stepper motors, to control the advancement and retractionof the wire. For example, such CSC welding systems dynamically control amotor direction (e.g., forward/reverse, clockwise/counter-clockwise) toturn a drive wheel of a welding wire feeder. As such, in such CSCsystems, when the wire is being fed toward the weld, the mechanicalmeans employed by conventional CSC systems have a relatively high levelof momentum in the feeding direction against which the mechanical meansmust counter in the opposite direction in order to retract the wire.

In addition, as described herein, conventional short circuit processesare relatively colder than pulse or spray MIG processes. One problemwith conventional short circuit transfer is that it generally depends ona “pinch effect” to separate the molten ball from the solid weldingwire. The pinch effect is driven by relatively high current. When theball separates, a plasma is re-ignited at this relatively high currentlevel. This makes for a relatively strong plasma force that pushes thepuddle away from the end of the welding wire, which can cause undesiredpuddle agitation. A short-by-short process (e.g., RMD™), which isdescribed in more detail in U.S. Pat. Nos. 6,326,591 and 6,800,832, bothof which are hereby incorporated by reference in their entireties, is analternative solution. In general, RMD™ still uses a pinch effect, butpredicts when the ball will separate from the welding wire, and reducesthe current before the separation occurs. This prediction method workswell, and is a close alternative. However, by comparison, the CSCprocess and the invention described herein do not need to use relativelyhigh current to separate the ball, so no prediction is required, and therisk of igniting a plasma at a relatively high current is eliminated. Inparticular, the reverse wire action removes the need for high currentsto “pinch” the molten ball off the end of the welding wire. Byeliminating this peak current, the stability of the process is increasedand a colder process can be achieved vs. conventional short circuit oreven RMD™ welding processes.

Certain embodiments of the present disclosure enable systems and methodsfor providing welding-type power using a welding wire feeder 24 thatprovides a welding wire electrode 28 to an arc, and a power source 54that provides power to the arc. The mechanical oscillation system 102described herein facilitates movement of the welding wire electrode 28toward and away from the arc. In certain embodiments, the controller 42controls the oscillating motion, controls the power source 54 to providea desired mean arc current, controls a welding wire spool, welding wiredrive assembly, and so forth, of the feeder 24 to control the averagewire feed speed of the welding wire electrode 28, or any combinationthereof. In addition, in certain embodiments, the controller 42 mayinclude various control modules, such as a mean arc current or arcvoltage control module to control a current or voltage of the weldingpower output of the power source 54 to a desired mean arc current orvoltage and/or a short detection feedback circuit.

In other embodiments, the control of the oscillating motion, control ofthe welding power output of the power source 54, and control of the wirefeed speed may not be controlled by the same controller 42. Rather, insuch embodiments, each may be set to run at a nominal setting, and eachmay be robust enough to respond to the expected responses of the othercomponents in the system 10. Such embodiments may result in reducedcomplexity of the system 10. For example, a strong and relatively fast(e.g., on the order of 20 kHz) constant voltage (CV) response during thearc phase and/or the short phase would modulate the current much fasterthan the short circuit frequency, and affect the burn off rate in orderto maintain a desired voltage.

Voltage is a strong indicator of arc length. In certain embodiments, thecontroller 42 may also automatically adapt on a slower time scale byadjusting nominal settings of the system 10. For example, if thecontroller 42 detects relatively short arc lengths during one or morearc phases, the nominal wire feed speed may be reduced, or the initialcurrent that the power source 54 uses for the arc phase or short phasecould be increased by the controller 42, or the oscillation frequencycould be changed by the controller 42 (e.g., by adjusting a speed of themotor 110 of the mechanical oscillation system 102). Each suchadjustment would tend to increase the average arc length.

In certain embodiments, a “synergic” control could be used by thecontroller 42, whereby in changing settings in one system, the nominalsettings of the other systems may also be changed. For example, if theaverage wire feed speed is increased, the power level of the powersource 54 may be increased (e.g., by increasing the voltage, current, orboth, of the power source 54) and/or the oscillation frequency of themechanical oscillation system 102 may be increased. In other words, ingeneral, the power level (e.g., voltage, current, or both) of the powersource 54 may be synchronized with the mechanical oscillation of themechanical oscillation system 102. For example, in certain embodiments,this could be done based on a table of matched settings. Adjusting onesetting sends an adjustment to the other components in the system 10.Synergic is a common term in the welding industry to describe a systemwhere by adjusting one parameter, many parameters are changed to idealnominal matched settings.

As such, the embodiments described herein facilitate relatively lowcost, yet improved performance, over conventional MIG welding processes.In particular, the mechanical oscillation system 102 described hereinenables relatively low cost oscillation of the welding wire electrode28, while still enabling CSC-style processes. Conventional MIG weldingprocesses, including CSC processes, can have short circuits ofapproximately 25 to over 200 times per second. The embodiments describedherein reduce the cost by reducing the mass that has to move as much aspossible. In certain CSC welding systems, a stepper motor has to changethe direction of the wire, a liner, wire feed rollers, and the motoritself. Of these, the inertia of the motor itself is arguably thegreatest. In contrast, in the embodiments described herein, the motor110 does not change direction, thus removing the requirement ofdecelerating an armature of the motor 110 and re-accelerating in theopposite direction at the oscillation frequency of the process (e.g.,between 20 and 200 cycles/second, in certain embodiments). Certain CSCwelding systems also require the cost and complexity of an “H-bridge”electrical drive, and a sophisticated controller to manage theelectrical drive, whereas the embodiments described herein do not.

In addition, oscillation at a substantially fixed frequency and/or witha substantially fixed travel distance simplifies the system 10 andreduces costs. In certain embodiments, an engraver or a low cost tattoomachine may be used as part of the mechanical oscillation system 102,and have a relatively fixed travel distance and a relatively fixedoscillation frequency. A relatively fixed travel distance and arelatively fixed oscillation frequency greatly reduces the cost of thesystem 10 (e.g., due at least in part to the tradeoff of flexibility forcost). Certain conventional CSC systems use stepper motors todynamically advance and reverse the wire, where the distance and speedof each individual forward and reverse motion are independent andindividually controlled. In contrast, in the embodiments describedherein, the oscillation distance of the mechanical oscillation system102 is relatively fixed, for example, by the size of the cam 108, andthe speed of the oscillation of the mechanical oscillation system 102 iscontrollable by, for example, adjusting the speed of the motor 110(i.e., to cause more or fewer shorts per second). In certainembodiments, a stepper motor could be used to offer more dynamicadvancement and retraction motion, but would likely increase the costand complexity of the system 10.

As described herein, the controller 42 may be used to control theelectrical power of the welding process to compensate for the relativelack of flexibility of the mechanical oscillation system 102. Inparticular, since the frequency and distance of the mechanicaloscillation are relatively fixed during operation of the mechanicaloscillation system 102, the controller 42 may control the electricalpower of the welding process (e.g., welding power delivered by the powersource 54) based on feedback relating to the welding process (e.g.,timing of phases of the welding process (such as a short circuit phase154, an arc re-establish phase 158, and so forth), timing of mechanicaloscillation of the mechanical oscillation system 102, and so forth). Forexample, since the cycles of the mechanical oscillation of themechanical oscillation system 102 remain relatively fixed duringoperation of the mechanical oscillation system 102 due to the relativelyfixed frequency and distance of the mechanical oscillation of themechanical oscillation system 102, the controller 42 may synchronize thedelivery of the welding power from the power source 54 with the cyclesof the mechanical oscillation of the mechanical oscillation system 102.For example, in certain embodiments, the controller 42 may periodicallycalibrate the delivery of the welding power from the power source 54based on feedback relating to the welding process (e.g., timing ofphases of the welding process (such as a short circuit phase 154, an arcre-establish phase 158, and so forth), timing of mechanical oscillationof the mechanical oscillation system 102, and so forth), for example,using sensor feedback (e.g., via the sensors 72 described herein) todetect the exact timing of a short circuit, an arc, and so forth, andadjust timing of transitions between states of the welding power basedon this feedback (see, e.g., FIGS. 8-10).

As described above with respect to FIG. 5, the welding wire electrode 28will have an oscillating motion in combination with a steady, butrelatively slower, motion of the welding wire electrode 28 movingforward at a fixed, yet slower, rate. As opposed to retracting thewelding wire electrode 28 by lifting the entire welding torch 20, orreversing the feed motor, the embodiments described herein force thewelding wire electrode 28 to traverse a relatively longer path. Assumingthe source of welding wire electrode 28 (e.g., the welding wire feeder24) and the weld puddle 32 are largely fixed locations, the welding wireelectrode 28 may be retracted from the puddle 32 by forcing the weldingwire electrode 28 to travel the relatively longer distance (see, e.g.,FIGS. 6A and 6B). In particular, the liner 100 has a substantially fixedlength. Pulling the liner 100 up and out of the contact tip of thewelding torch 20 will, in effect, create a longer liner 100. When theliner 100 changes direction, excess space between the liner 100 and thewelding wire electrode 28 must be absorbed. This small distance must beadded to the amount that the liner 100 must move. A minimal amount ofexcess space between the liner 100 and the welding wire electrode 28 isideal.

As described above, the mechanical oscillation system 102 may have asubstantially fixed oscillation frequency and/or a substantially fixedoscillation travel distance to simplify the system 10 and reduces costsof the system 10. As described herein, properties referred to as“substantially fixed” or “relatively fixed” are intended to describeproperties that do not vary more than a substantially small amount(e.g., less than 5 percent, less than 4 percent, less than 3 percent,less than 2 percent, less than 1 percent, or even less) duringoperation. It will be appreciated that, in certain embodiments, a speedof the motor 110 of the mechanical oscillation system 102 may beadjusted by the controller 42, thereby adjusting the frequency of themechanical oscillation. However, once the speed of the motor 110 isadjusted by the controller 42, the frequency of the mechanicaloscillation will remain substantially fixed during operation of themechanical oscillation system 102. In contrast, in certain embodiments,the distance of the mechanical oscillation remains substantially fixedat all times due at least in part to inherent physical characteristicsof the components of the mechanical oscillation system 102.

One problem with a substantially fixed oscillation frequency and asubstantially fixed oscillation travel distance is that either of theseproperties may not actually be in synch with the puddle 32 and theactual ball detachment. However, as described herein, the controller 42may dynamically adjust the electrical power (e.g., voltage, current, orboth) generated by the power source 54 to compensate for the relativelack of sophistication (i.e., lack of flexibility of operation via widerranges of oscillation frequency and oscillation travel distance) of themechanical oscillation system 102. In particular, the electrical powergenerated by the power source 54 is controlled by the controller 42based on feedback relating to the welding process (e.g., timing ofphases of the welding process (such as a short circuit phase 154, an arcre-establish phase 158, and so forth), timing of mechanical oscillationof the mechanical oscillation system 102, and so forth). The simplestsolution would be to use a conventional constant current (CC) weldingpower source as the power source 54. In such an embodiment, if theoscillation retraction distance is large enough, the welding currentfrom the power source 54 may be set at a relatively fixed level justhigh enough to melt the welding wire electrode 28 one ball 34 at a timebut still relatively low such that not much puddle agitation is causedand such that molten material will not be ejected from the puddle 32 oroff the end of the welding wire electrode 28 (i.e., commonly referred toas spatter). In certain embodiments, a control loop may be used by thecontroller 42 to dynamically adjust the average current and/or theaverage wire feed speed to maintain a steady and stable process.

In certain embodiments, the process may be improved over a relativelyconstant current process by implementing dynamic changes to the weldingvoltage and/or current (i.e., the “wave shape”). As described above,examples of wave shaping include Accu-Pulse™, RMD™, and CSC weldingprocesses. Again, it is desirable to enable a relatively simple and lowcost system 10 and, as such, the wave shape changes that are implementedby the controller 42 may include increasing the current after thewelding wire electrode 28 has separated from the puddle 32 (and theplasma has been re-ignited). Doing so will help to form the next ball34, help ensure that possible puddle oscillations do not re-attach tothe welding wire electrode 28, and help increase the amount of weldingwire electrode 28 that can be deposited as this is a “safe” place to addenergy to the process without increasing the risk of an unstableprocess. In addition, the wave shape changes that are implemented by thecontroller 42 may include reducing the current as the welding wireelectrode 28 is about to touch the puddle 32. Doing so will help reducethe chances of the welding wire electrode 28 burning away as its tryingto touch the puddle 32, help reduce the chances of the welding wireelectrode 28 and the molten ball 34 touching the puddle 32 and being“rejected” by a poorly timed pinch event. In addition, the wave shapechanges that are implemented by the controller 42 may include reducingthe current as the welding wire electrode 28 is about to separate fromthe molten puddle 32. Doing so will help reduce the force of the plasmaas it re-ignites. Reducing this force (i.e., going from no plasma toplasma) reduces puddle agitation, reduces spatter, and helps make theprocess more stable.

In certain embodiments, if the arc has not re-established and theretraction is over or about to be over, the controller 42 may increasethe current to force the pinching of the molten column between thepuddle 32 and the welding wire electrode 28. In certain embodiments, ifthe welding wire electrode 28 gets buried into the puddle 32 and thecontroller 42 determines that no retraction of the mechanicaloscillation system 102 will re-ignite the plasma, then a conventionalpinch event may be required. In such an event, the controller 42 mayadjust the wave shape to include a relatively high current event toliquefy the welding wire electrode 28 and/or pinch the liquid area ofthe welding wire electrode 28 and/or the puddle 32, and re-ignite thearc. In addition, in certain embodiments, if a pinch event wouldgenerate too much force for a relatively delicate 3D part, thecontroller 42 may stop the process and require manual resetting of thesystem 10.

FIG. 8 illustrates time series of wire feed speed (WFS) of the weldingwire electrode 28 caused by the mechanical oscillation system 102 (i.e.,trace 132), voltage (V) of the electrical power generated by the powersource 54 (i.e., trace 134), and current (I) of the electrical powergenerated by the power source 54 (i.e., trace 136), in accordance withan exemplary CSC wave shape implemented by the controller 42. Asillustrated in FIG. 8, and as described in greater detail herein, thewire feed speed of the welding wire electrode 28 generally oscillatesbetween a positive feed rate 138 and a negative feed rate 140 (i.e.,during retraction), wherein the positive feed rate 138 has a magnitudethat is greater than the negative feed rate 140 such that the weldingwire electrode 28 is advanced over time, as illustrated in FIG. 5. Theaxes 142 for each trace 132, 134, 136 are intended to represent zerovalues for each respective parameter, i.e., wire feed speed, voltage,and current. FIG. 8 shows that the positive wire feed speed area (e.g.,corresponding to the positive feed rate 138) is higher above the axis142 than the negative wire feed speed area (e.g., corresponding to thenegative feed rate 140) is below the axis 142. Again, this is to showthat the total wire feed speed is a combination of the constant forwardwire feed speed plus the oscillations caused by the mechanicaloscillation system 102.

As illustrated in FIG. 8, the current is held relatively low during ashort (e.g., intervals 144). After the short clears (e.g., intervals146), the current is increased for a short time (e.g., between 0.5-5.0milliseconds, in certain embodiments) to form a ball 34. In certainembodiments, this arc phase may have a constant voltage (CV)characteristic, which has an added advantage of increasing or decreasingthe current of the ball-forming peak 148 such that larger or smallerballs 34 are formed depending on how close the welding wire electrode 28is to the puddle 32 (e.g., the arc length). This will tend to helpbalance the burn-off rate with the average forward wire feeding rate.The CV characteristic may be achieved with the duration of time of theball forming pulse or its amplitude.

Then, after the ball 34 is formed, the current may be reduced to arelatively low level 150 (e.g., intervals 152). In certain embodiments,this may have a constant current (CC) characteristic. However, in otherembodiments, a CV characteristic at a relatively low voltage level maybe implemented, which may tend to help match the incoming average wirefeed rate with the burn-off rate. Ideally, this relatively low current150 would be such that there is minimal force from the plasma betweenthe ball 34 and the puddle 32 as the welding wire electrode 28 getsclose to the puddle 32, and such that there is minimal spatter createdor ball rejection when the ball 34 touches the puddle 32. The currentwill be held relatively low waiting for the welding wire electrode 28 tobe retracted from the puddle 32 by the mechanical oscillation system102, leaving the ball 34 in the puddle 32. In certain embodiments, apulse of current during the short (e.g., intervals 144) may beimplemented, which may tend to increase resistive heating of the weldingwire electrode 28, but which may also produce spatter if the shortclears while still at the relatively high current level (e.g., peaks148). In certain embodiments, the amplitude of this pulse current may beinfluenced by a constant voltage (CV) control loop, whose amplitude ortime may be limited by the controller 42 to ensure the current is not ata relatively high level when the short clears.

It should be noted that the constant voltage (CV) states tend to give acertain amount of dynamic power to help the system 10 match the meltrate with the average wire feed speed. This dynamic melting improves therobustness of the process. In contrast, a process where the power isentirely constant current (CC) is relatively more difficult to match toa fixed wire feed speed. FIG. 9 illustrates another set of time seriesof wire feed speed (WFS) of the welding wire electrode 28 caused by themechanical oscillation system 102 (i.e., trace 132), voltage (V) of theelectrical power generated by the power source 54 (i.e., trace 134), andcurrent (I) of the electrical power generated by the power source 54(i.e., trace 136), in accordance with another exemplary CSC wave shapeimplemented by the controller 42. In particular, FIG. 9 illustrates oneoscillation of the welding wire electrode 28 (e.g., one cycle of thepositive feed rate 138 and the negative feed rate 140) for each balltransfer. It is entirely possible to have multiple oscillations of thewelding wire electrode 28 for one ball transfer. In particular, if theball 34 formation pulse melts enough of the welding wire electrode 28,then it may take a couple of oscillation cycles of the mechanicaloscillation system 102 before the welding wire electrode 28 has advancedfar enough to make contact with the puddle 32 again. In general, theprimary function of the mechanical oscillation system 102 is to pull thewelding wire electrode 28 out of the puddle 32, while leaving the ball34 behind.

Returning to FIG. 9, during a short circuit state (e.g., interval 154),as the welding wire electrode 28 is being advanced at the positive feedrate 138, the voltage may be detected. For example, in certainembodiments, the sensors 72 described herein may include voltage-sensingcircuitry that detects the voltage, and communicates the detectedvoltage to the controller 42 (e.g., such that the controller 42 candetermine that the short circuit state 154 has been initiated, forexample, by detecting a substantial decrease in the voltage). Forreference, in GMAW welding, a short circuit phase will generally have avoltage of 10-15 volts lower than an arc phase. That is, it takes about10 volts to ionize the welding gas to create the arc. During the shortcircuit state 154, the current is held at a relatively low constantcurrent (CC) level 156 (e.g., less than 50 amps, or between 5-30 amps,in certain embodiments) so as to not cause much spatter or puddleagitation when the short clears. In certain embodiments, once the shortcircuit state 154 is established, in addition to synchronizing thewelding power to the mechanical oscillation, the controller 42 may alsosend a command to the mechanical oscillation system 102 to retract thewelding wire electrode 28 at the negative feed rate 140. In certainembodiments, an index sensor could be used to provide explicit feedbackto the controller 42 of the position of the welding wire electrode 28(i.e., whether the welding wire electrode 28 is in a retracted oradvanced position). In certain embodiments, the sensors 72 may be usedby the controller 42 to determine when the short circuit state 154 hasended, for example, by detecting the voltage, thereby allowing thecontroller 42 to determine that the short circuit has cleared based on asubstantial increase in the voltage.

Subsequently, during an arc re-establish state (e.g., interval 158),which occurs directly after the short circuit state 154, the controller42 holds the current at the relatively low constant current (CC) level156 for a short period of time (e.g., between 100-300 milliseconds,between 150-250 milliseconds, or approximately 200 milliseconds, incertain embodiments) such that the arc may be re-established with arelatively low current while the welding wire electrode 28 is beingretracted.

Once the arc is re-established, and while the welding wire electrode 28continues to be retracted, during a ball formation state (e.g., interval160), which occurs directly after the arc re-establish state 158, thecontroller 42 increases the current to a relatively higher current level162 to burn the welding wire electrode 28 back away from the puddle 32and to form the next ball 34. As illustrated, in certain embodiments, aconstant current (CC) ramp 164 may be implemented by the controller 42to drive the relatively quick jump in current. In certain embodiments,the degree of the CC ramp 164 (i.e., the rate of increase of the currentfrom the relatively low constant current level 156 to the peak currentlevel 162) may be determined by the controller 42 based at least in parton the size (e.g., diameter) or particular alloy of the welding wireelectrode 28 and/or the average wire feed speed. Once the peak currentlevel 162 is reached, the controller 42 may implement a constant voltage(CV) control loop on the current to give the process additionalrobustness. In certain embodiments, the peak current level 162 may belimited by the controller 42 so as to avoid transitioning into a spraymode. In certain embodiments, the peak current level 162 may be lessthan 250 amps, less than 200 amps, or even less (e.g., between 150-200amps, in certain embodiments). In addition, the peak current level 162is limited by the controller 42 to minimize the force that the plasmahas on the puddle 32 (i.e., to limit the penetration and puddleagitation).

After a fixed amount of time in the ball formation state 160 (e.g., lessthan 5 milliseconds, less than 2 milliseconds, less than 1 millisecond,or even less, in certain embodiments), and while the welding wireelectrode 28 continues to be retracted, during a background state (e.g.,interval 166), which occurs directly after the ball formation state 160,the controller 42 decreases the current down from the peak current level162 to a relatively low current level 168 to begin the background state166. Once the relatively low background current level 168 is reached,the controller 42 may switch to a constant voltage (CV) control loop forimproved process robustness. In certain embodiments, the backgroundcurrent level 168 may be limited to less than 50 amps, or between 5-30amps, so that the plasma does not push the puddle 32 away too much fromthe next short, so as to not make a ball 34 that is too big, and to notput too much heat into the puddle 32. In certain embodiments, once therelatively low background current level 168 is reached, in addition tosynchronizing the welding power to the mechanical oscillation, thecontroller 42 may also send a command to the mechanical oscillationsystem 102 to begin advancing the welding wire electrode 28 at thepositive feed rate 138 again. Once the background state 166 iscompleted, the cycle will repeat again (i.e., with the next shortcircuit state 154).

The CSC process implemented by the controller 42, as illustrated in FIG.9, may include several alternative features in certain embodiments. Forexample, in certain embodiments, all of the states 154, 158, 160, 166 ofthe CSC process illustrated in FIG. 9 may be either constant current(CC) or constant voltage (CV). For example, all of the states 154, 158,160, 166 could be CC, but the process would not be quite as robust.Alternatively, just one of the states 154, 158, 160, 166 could be CV togive some amount of dynamic melting to help the system 10 match the meltrate with the average wire feed speed. In addition, in certainembodiments, the controller 42 may use a running average voltage toapproximate arc length, and then drive the duration of the ballformation state 160 based at least in part on the running averagevoltage. In other words, if the arc length is determined by thecontroller 42 to be shorter than desired (e.g., indicating the burn-offis not keeping up with the wire feed speed), then the controller 42could change the duration of the ball formation state 160 to melt moreincoming welding wire electrode 28 to generate a bigger ball 34 for thenext ball deposit and/or increase the frequency of oscillation todeposit more balls 34 per unit time. In addition, in certainembodiments, the controller 42 may implement mostly CC power, and changethe speed of the incoming welding wire electrode 28. In other words, ifthe average voltage is determined by the controller 42 to be too low(e.g., indicating a relatively low average arc length), then thecontroller 42 could reduce the wire feed speed from the feeder 24 toincrease the arc length. Doing so would tend to match the feed rate withthe melting rate. However, since the dynamic control of the motor 110 ofthe mechanical oscillation system 102 is typically slower thanelectrical control loops, adjusting the wire feed speed in this mannermay not enable as accurate control.

In addition, in certain embodiments, the controller 42 may implement aconventional CV control loop, but with certain limits imposed. FIG. 10illustrates another set of time series of wire feed speed (WFS) of thewelding wire electrode 28 caused by the mechanical oscillation system102 (i.e., trace 132), voltage (V) of the electrical power generated bythe power source 54 (i.e., trace 134), and current (I) of the electricalpower generated by the power source 54 (i.e., trace 136), in accordancewith another exemplary CSC wave shape implemented by the controller 42,wherein a conventional CV control loop is used with certain limits.Specifically, as illustrated in FIG. 10, the controller 42 may allow theCV process to run “normally” (i.e., in a conventional manner), but limitthe current during the short circuit state 154 to a lower current level170 (approximately 10-100 amps) than the background current level 168(approximately 30-150 amps), and possibly also limit the peak currentlevel 162 (approximately 100-300 amps). As illustrated in FIG. 10, incertain embodiments, as opposed to the CC ramp 164 discussed above withrespect to FIG. 9, a constant voltage (CV) ramp 172 may be implementedby the controller 42 to drive the current from the relatively lowershort circuit current level 170 to the peak current level 162 in asmoother, more asymptotic manner than the CC ramp 164. In practice, theintegral component of a conventional PID control loop will be “pumpedup” after being held low during a short. As such, it will naturally riseonce it is allowed to do so at the end of the short. After the ball 34is formed, the voltage control loop will be satisfied, and the errorwill go down, as will the current. In general, a CV control loop is asimple way to achieve a robust design with minimal effort.

As described herein, a recognized drawback of the relatively fixedretraction/advance and the relatively fixed frequency of the mechanicaloscillation system 102 is that it may be relatively difficult tosynchronize with the puddle 32 and actual detachment of the ball 34.Therefore, with this in mind, the embodiments of the controller 42described herein control the electrical power generating the plasma andmelting the welding wire electrode 28 to compensate for the lack ofsophistication of the mechanical oscillation system 102. In general, theelectrical power (e.g., welding power) is a slave to the mechanicalprocess performed by the mechanical oscillation system 102. The simplestsolution would be to use a conventional constant current (CC) weldingpower source (e.g., as the power source 54). In other words, if theretract distance is enough, the welding current can be set to, and stayat, a relatively fixed level. This relatively fixed current level wouldhave to be high enough to melt the welding wire electrode 28 one ball 34at a time. The relatively fixed current level would be relatively lowsuch that it does not cause much puddle agitation or eject moltenmaterial from the puddle 32 or off the end of the welding wire electrode28 (i.e., commonly referred to as spatter). However, in suchembodiments, the CC melt rate would have to match the wire feed speed.In such embodiments, a slight “droop” in the CC response of the weldingpower source (e.g., the power source 54) and/or a voltage-sensing feeder(e.g., the feeder 24) would make this CC method more robust insofar asdroop in a CC control loop means a slight reduction in the current asthe voltage increases.

In certain embodiments, the process may be improved with simple dynamicchanges to the welding current, as illustrated in FIGS. 8-10. With agoal of a relatively simple and low cost system 10, the wave shapechanges implemented by the controller 42, as illustrated in FIGS. 8-10,are relatively minimal. For example, increasing the current after thewelding wire electrode 28 has separated from the puddle 32 will help toform the next ball 34, help ensure that possible puddle oscillations donot re-attach to the welding wire electrode 28, and help increase theamount of the welding wire electrode 28 that can be deposited, as thisis a “safe” place to add energy to the process without increasing therisk of any instabilities. In addition, reducing the current as thewelding wire electrode 28 is about to touch the puddle 32 will helpreduce the chances of the welding wire electrode 28 burning away as itis trying to touch the puddle 32, and will help reduce the chances ofthe welding wire electrode 28 and the molten ball 34 touching the puddle32 and being “rejected”. In addition, reducing the current as thewelding wire electrode 28 is about to separate from the molten puddle 32will help reduce the force of the plasma as it re-ignites (i.e., duringthe arc re-establish state 158). Reducing this force (e.g., going fromno plasma to plasma) reduces puddle agitation, and helps make theprocess more stable. In general, if the arc has not re-established, andthe retraction of the welding wire electrode 28 is over or about to beover, the current must be increased by the controller 42 to force thepinching of the molten column between the puddle 32 and the welding wireelectrode 28. In certain embodiments, the current could be increased bythe controller 42 during the short circuit state 154 to gain someresistive heating of the welding wire electrode 28. Doing so would helpput heat into the welding wire electrode 28 without also putting moreheat into the puddle 32, thereby reducing the need for time spent in theplasma, and thus reducing the heat into the puddle 32, which may beadvantageous for building up of a small part, for example.

Again, in certain embodiments, the current is held relatively low by thecontroller 42 during the short circuit state 154. After the shortclears, the current may be increased by the controller 42 (e.g., duringthe ball formation state 160) for a relatively short time (e.g., lessthan 40 milliseconds, less than 5 milliseconds, less than 1 millisecond,or even less, in certain embodiments) to form the ball 34. In certainembodiments, the ball formation state 160 would include a constantvoltage (CV) characteristic, thus having an added advantage ofincreasing or decreasing the ball forming peak current level 162 suchthat larger or smaller balls 34 are formed depending on how close thewelding wire electrode 28 is to the puddle 32 (e.g., the arc length).The CV characteristic will tend to help balance the burn-off rate withthe average forward wire feeding rate. In certain embodiments, the CVcharacteristic could be achieved by the controller 42 by adjusting theduration of time of the ball formation state 160 or its amplitude.

Then, after the ball 34 is formed, the current may be reduced by thecontroller 42 to a relatively low background current level 168. In theembodiment illustrated in FIG. 8, this current reduction would have aconstant current (CC) characteristic. However, in the embodimentsillustrated in FIGS. 9 and 10, this current reduction would have aconstant voltage (CV) characteristic, which would tend to help match theincoming average wire feed rate with the burn-off rate. In general, therelatively low background current level 168 would be held low enough bythe controller 42 such that there is minimal force from the plasma ontothe puddle 32 as the welding wire electrode 28 gets close to the puddle32, and that there is minimal spatter created when the ball 34 touchesthe puddle 32. In addition, the relatively low background current level168 would be maintained as the controller 42 waits for the welding wireelectrode 28 to be retracted from the puddle 32, leaving the ball 34 inthe puddle 32.

In certain embodiments, the controller 42 may cause a pulse of currentduring the short circuit state 154, which would tend to increase theresistive heating of the welding wire electrode 28, but may also producemore spatter if the short clears while still at the relatively higherpulsed current level. In certain embodiments, a “safety net” shortclearing state may be implemented by the controller 42 to handlesituations when the welding wire electrode 28 is not retracted enoughfrom the puddle 32 (e.g., when the short circuit state 154 has aduration that is longer than one or two full mechanical oscillationcycles of the welding wire electrode 28 caused by the mechanicaloscillation system 102). Such a short clearing state may includestopping the process altogether, or implementing a relatively highcurrent short clearing pulse of energy.

In the interest of describing the operation of the system 10 describedherein, a specific example will be presented. In particular, assumingthat the welding wire electrode 28 has a positive net total wire feedspeed (i.e., including both the forward feeding and the retraction) of120 inches per minute, or 2 inches per second, which is relatively slowfor wire feed rates, and that the mechanical oscillation system 102oscillates the welding wire electrode 28 at a substantially fixed rateof 60 oscillations per second, then the welding wire electrode 28vibrates up/down 60 times for every 2 inches traversed. As such, ingeneral, the welding wire electrode 28 should burn off 60 molten metalballs 34 for every 2 inches traversed. Accordingly, the welding wireelectrode 28 is advanced such that each ball 34 will consume about 2/60(i.e., approximately 0.0333) of an inch of the welding wire electrode28.

In addition, if the mechanical oscillation system 102 causes the weldingwire electrode 28 to oscillate at a substantially fixed rate of 60oscillations per second, and if a duration of each phase of forwardmotion of the welding wire electrode 28 is approximately equal to aduration of each phase of retraction of the welding wire electrode 28,then the durations of the phases of forward motion and retraction of thewire electrode 28 are equal to approximately 1/120 seconds (i.e.,approximately 8.333 milliseconds). At a rate of 2 inches per second ofsteady forward advancement of the welding wire electrode 28 from thefeeder 24, the welding wire electrode 28 moves approximately 0.01667inches (i.e., 2 inches/second×0.008333 second) of welding wire electrode28 while the welding wire electrode 28 is retracting. In general, thewelding wire electrode 28 must retract approximately 0.01667 inches plusthe distance needed to break the liquid bridge (for example, thediameter of a single ball 34 may be estimated to be approximately 0.05inch). Therefore, the total retract distance of the welding wireelectrode 28 must be a minimum of approximately0.05+0.01667=approximately 0.06667 inches. In general, reducing theamount of time the retraction takes reduces the amount of welding wireelectrode 28 that will be advanced while retraction occurs.

When the plasma re-ignites, it will melt the welding wire electrode 28,increasing the distance that the molten ball 34 must be moved forward toreconnect with the puddle 32. Assuming that a new ball 34 has formed,and approximately 0.0333 inches of the welding wire electrode 28 hasbeen melted to form a 0.05 inch diameter ball 34, by moving more than0.1 inch forward or retracting, the molten ball 34 will be nearlyguaranteed to reconnect with or separate from the puddle 32. In thisscenario, this distance is twice the diameter of the ball 34, and is arelatively small distance to travel.

A diameter of the ball 34 that is slightly larger than the diameter ofthe welding wire electrode 28 is common for other welding processes aswell. In general, the velocity of the retraction should be significantlyfaster than the velocity of the forward motion of advancement. Inaddition, the relatively fixed travel distance of the retraction shouldbe enough to pull the welding wire electrode 28 out of the molten puddle32. In addition, the surface tension will tend to cause the molten metalfrom the puddle 32 to “stick” to the welding wire electrode 28, so thetravel distance of the retraction should be enough to overcome thissurface tension.

In general, electrical current flowing through a liquid conductor willcause the liquid conductor to constrict. This is called the “pincheffect”. With conventional MIG welding processes, relatively high peakcurrents are used to separate the wire from the liquid puddle. However,this relatively high current then also re-ignites the plasma with arelatively strong force that agitates the molten puddle, and adds acertain amount of volatility to the process. Ideally, the plasma isre-ignited at a relatively low current such that little agitationoccurs.

In the embodiments described herein, by retracting the welding wireelectrode 28, the welding wire electrode 28 will separate from thepuddle 32. If the welding wire electrode 28 does not completelyseparate, more electrical current can be added to drive an electricalpinch. Since the retraction likely narrows the liquid column, thecurrent required would still be less than without the retraction. With arelatively small diameter wire, the liquid ball 34 (and subsequentliquid column between the end of the welding wire electrode 28 and thepuddle 32) will have a smaller diameter, and shorter retraction can beused. Speed is not necessarily a critical performance requirement for alow cost system 10. In addition, a smaller diameter welding wireelectrode 28 will produce a smaller ball and a narrower puddle 32, whichwill provide greater resolution for the finished part. In general, speedof producing the part may be sacrificed for resolution, accuracy, andreduced penetration.

Certain alternatives may be used for the system 10 described herein. Forexample, instead of using the CSC processes described herein, in certainembodiments, MIG welding processes may be implemented by the controller42 and the power source 54. In such embodiments, the mechanicalretraction caused by the mechanical oscillation system 102 ensuresbetter starts and fewer problems. Furthermore, in other embodiments, RMDwelding processes may also be implemented by the controller 42 and thepower source 54. In such embodiments, the RMD process may be optimizedby the controller 42 for the particular application. In addition, inother embodiments, a modified submerged-arc welding (SAW) process may beimplemented by the controller 42 and the power source 54. In suchembodiments, the flux would allow for different metallurgicalcharacteristics in the finished parts. In all embodiments describedherein, different alloys of the welding wire electrode 28 may be used,especially cored wires, to achieve unique metallurgical characteristicsin the finished parts.

In general, the embodiments described herein are intended to enhance thedetachment of the ball 34 via the relatively low cost mechanicaloscillation system 102. In certain embodiments, the mechanicaloscillation system 102 may send a shock wave down the welding wireelectrode 28 like a pneumatic drill. Such vibration in the liquid columnmay make the liquid column begin to constrict. Once the constrictionstarts, if there is adequate current, the pinch effect will take over.

In certain embodiments, an additive welding process to form a 3D partwould put one weld bead on top of previous weld beads to form a part. Ifthe base is fused to the first weld bead, then a base must be used. Insuch embodiments, a conductive and chilled plate, such as a water-cooledcopper block, may be used. Such a block would not fuse with the weldbead. This would allow more flexibility in forming the part,particularly the first layer and the bottom layer.

Again, the embodiments described herein enable a relatively low costsystem 10 that includes a mechanical oscillation system 102 that has arelatively fixed travel distance and a relatively limited oscillationfrequency range for oscillating the welding wire electrode 28 betweenforward motion and retraction. The relative lack of sophistication ofthe mechanical oscillation system 102, which helps reduce the cost ofthe system 10, is compensated for by the controller 42 implementing theCSC processes described herein via the power source 54.

The embodiments described herein may also facilitate better arc starts.Arc starting has been a perennial problem in arc welding usingconsumable electrodes, and its economics are amplified in short stitchwelding, such as in automotive seats. Typically, the wire is fed at aslow feed rate (called run-in speed) until a short circuit occurs.Thereafter, a surge of current is output from the welding power sourceto ignite the arc or blow away the short circuit like a fuse, hopefullyresulting in arc ignition. However, depending on the condition of theinitial contact between wire and the workpiece, the fuse explosion andarc ignition may not be peaceful. If the contact resistance is low, forexample when the wire end is not sharp, the wire stubs out and theentire wire extended from the contact tip may be broken off like aflying baton, or the wire may just heat up and bend like a noodle.Remedies for better arc start do exist to have graceful arc ignition butalso carries penalties. For example, slower run-in speed wastes robotcycle time; wire retract start requires expensive motorized torch, andwire sharpening pulse at arc end may yield crater defect.

The system 10 described herein may be used to facilitate initialwire-to-workpiece contact (or “scratch starting”) due at least in partto the oscillation of the welding wire electrode 28 that generated bythe mechanical oscillation system 102. In general, the oscillation ofthe welding wire electrode 28 may be manipulated such that slightcontact is created between the welding wire electrode 28 and theworkpieces 16, 18, thereby increasing the contact resistance R andmagnifying the I²R (i.e., current (I) squared times resistance (R))heating of the tip of the welding wire electrode 28 that contacts theworkpieces 16, 18. With the increased resistance R, the same current Imay produce an increased heating effect to ignite the arc.

FIG. 11 is a flow chart that depicts an arc starting process 174 thatmay be implemented by the system 10 described herein in certainembodiments. The arc starting process 174 may begin when an arc startcommand (e.g., the trigger 80 of the welding torch 20 being pulled by anoperator in manual welding, or a robot cycle start button being pushedin robotic welding, for example) has been received by the controller 42(block 176). Once the arc start command has been received by thecontroller 42, the controller 42 may send a command to the mechanicaloscillation system 102 to start the oscillation of the welding wireelectrode 28 (block 178). In addition, the controller 42 may send acommand to the feeder 24 to begin feeding of the welding wire electrode28 to the welding torch 20 (block 180). Then, the one or more sensors 72may be used to sense whether an arc between the welding wire electrode28 and the workpieces 16, 18 has been established (block 182). Forexample, in certain embodiments, the sensors 72 may includevoltage-sensing circuitry and/or current-sensing circuitry, which may beused to detect when the voltage and/or current cross a predeterminedthreshold, such as 14 volts, for example. Upon determination that thearc establishment condition has occurred, the controller 42 may send acommand to the mechanical oscillation system 102 to stop the oscillationof the welding wire electrode 28 (block 184), which will reduce the dutycycle requirement on the motor 110 of the mechanical oscillation system102, thereby reducing the cost and weight requirement of the mechanicaloscillation system 102. Then, the controller 42 may send a command tothe feeder 24 to ramp the speed of the feeding of the welding wireelectrode 28 up to a desired welding wire feed speed (block 186), whichmay be set via the operator interface 78.

The arc starting process 174 described with reference to FIG. 11, whichmay be implemented by the system 10 described herein, may provideseveral advantages over conventional arc starting methods. For example,the arc starting process 174 provides more reliable arc starts thanconventional arc starting methods, thereby causing less downtime andproducing lower amounts of spatter. These two advantages are veryimportant in applications with short welds and many arc starts. Inaddition, the arc starting process 174 costs relatively less thanconventional arc starting methods, due at least in part to theimplementation of the relatively low cost mechanical oscillation system102. In addition, the arc starting process 174 reduces cycle time ininstances where the run-in speed may be increased while still producingreliable arc starts. In addition, the arc starting process 174 reduceselectromagnetic interference (EMI) and electromagnetic fields (EMF) ininstances where relatively lower arc currents are required while stillproducing reliable arc starts. In addition, the arc starting process 174increases contact tip life because of less electrical erosion that mayotherwise result from relatively lower arc current surges whileestablishing the arc. In addition, the arc starting process 174described with reference to FIG. 11, which may be implemented by thesystem 10 described herein, may provide advantages relating to arcstarting in several applications including, but not limited to, gasmetal arc welding (GMAW), including MIG welding; SAW; wire brazing; weldoverlaying, including cladding and/or hardfacing; multiple-wireGMAW/SAW; GMAW-laser hybrid welding; and so forth.

While only certain features of the present disclosure have beenillustrated and described herein, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the present disclosure.

The invention claimed is:
 1. A system comprising: a welding toolconfigured to receive a welding wire from a wire feeder, to receivewelding power from a power source, and to supply the welding wire to aworkpiece during a welding process; and a mechanical oscillation systemconfigured to mechanically oscillate a structural component toward andaway from the workpiece, wherein the structural component is external tothe wire feeder and the power source.
 2. The system of claim 1, whereinthe structural component is at least partially disposed within thewelding tool.
 3. The system of claim 1, wherein the welding toolcomprises the mechanical oscillation system and the structuralcomponent.
 4. The system of claim 1, wherein the welding tool is ahandheld welding tool.
 5. The system of claim 1, wherein the weldingtool is a robotic welding tool.
 6. The system of claim 1, wherein thestructural component comprises a liner.
 7. The system of claim 1,wherein the welding process comprises a metal inert gas (MIG) weldingprocess.
 8. The system of claim 1, wherein the welding wire extendsthrough the structural component.
 9. The system of claim 1, whereinmechanical oscillation of the structural component has a substantiallyfixed travel distance.
 10. The system of claim 1, wherein mechanicaloscillation of the structural component has a substantially fixedfrequency.
 11. The system of claim 1, wherein the mechanical oscillationsystem comprises a motor and a mechanical linkage assembly coupled tothe motor, wherein the mechanical linkage assembly is fixedly attachedto the structural component.
 12. The system of claim 11, wherein thewelding tool comprises a liner extending into the structural component,the welding wire extends through the liner, and the structural componentis directly coupled to the liner.
 13. The system of claim 11, whereinthe mechanical linkage assembly comprises a cam coupled to the motor,and a piston coupled to the cam, wherein the piston is fixedly attachedto the structural component.
 14. A system comprising: a welding toolconfigured to receive a welding wire from a wire feeder, to receivewelding power from a power source, and to supply the welding wire to aworkpiece during a welding process; a mechanical oscillation systemconfigured to mechanically oscillate a structural component toward andaway from the workpiece, wherein the structural component is external tothe wire feeder and the power source; and control circuitry configuredto control the welding power based on feedback relating to the weldingprocess.
 15. The system of claim 14, wherein the control circuitry isconfigured to control the welding power based at least in part onfeedback relating to timing of a short circuit that occurs between thewelding wire and the workpiece during the welding process.
 16. Thesystem of claim 15, wherein the control circuitry is configured todetermine when the short circuit occurs based at least in part onfeedback received from a sensor that detects a voltage level of thewelding power.
 17. The system of claim 15, wherein the control circuitryis configured to hold a current level of the welding power substantiallyconstant for a time period of between 100-300 milliseconds after theshort circuit ends before increasing the current level of the weldingpower.
 18. The system of claim 15, wherein the control circuitry isconfigured to increase a current level of the welding power to a peakcurrent level after the short circuit ends.
 19. The system of claim 18,wherein the control circuitry is configured to increase the currentlevel to the peak current level using a constant current (CC) ramp. 20.The system of claim 18, wherein the control circuitry is configured todetermine a rate of increase of the current level to the peak currentlevel based at least in part on a diameter of the welding wire, anaverage wire feed speed of the welding wire, or a combination thereof.21. The system of claim 18, wherein the control circuitry is configuredto increase the current level to the peak current level in an asymptoticmanner.
 22. The system of claim 18, wherein the peak current level isless than 250 amps.
 23. The system of claim 18, wherein the controlcircuitry is configured to decrease the current level from the peakcurrent level to a background current level.
 24. The system of claim 23,wherein the background current level is less than 50 amps.
 25. Thesystem of claim 23, wherein the control circuitry is configured tomaintain the current level at the peak current level for a fixed amountof time before decreasing the current level to the background currentlevel.
 26. The system of claim 23, wherein the control circuitry isconfigured to maintain a voltage level of the welding powersubstantially constant when the background current level is reached. 27.The system of claim 14, wherein the control circuitry is configured tocontrol the welding power based at least in part on feedback relating totiming of a welding arc that occurs between the welding wire and theworkpiece during the welding process.
 28. The system of claim 14,wherein the control circuitry is configured to control the welding powerbased at least in part on feedback relating to the mechanicaloscillation of the structural component.
 29. The system of claim 14,comprising control circuitry configured to control the mechanicaloscillation of the structural component.
 30. The system of claim 14,wherein the control circuitry is configured to switch between a constantcurrent (CC) mode of operation and a constant voltage (CV) mode ofoperation based at least in part on the feedback relating to the weldingprocess.
 31. A system comprising: a welding tool configured to receive awelding wire and to supply the welding wire to a workpiece, wherein thewelding tool comprises a mechanical oscillation system configured tomechanically oscillate a structural component of the welding tool towardand away from the workpiece; and control circuitry configured to receivean arc start command, to control the mechanical oscillation system tostart oscillation of the structural component, to control a wire feederto begin feeding the welding wire, to determine whether an arc betweenthe welding wire and the workpiece is initiated based at least in parton feedback received from a sensor, to control the mechanicaloscillation system to stop oscillation of the structural component oncethe arc is determined to be established, and to control the wire feederto increase a wire feed speed of the welding wire to a desired wire feedspeed.
 32. The system of claim 31, wherein the sensor comprisesvoltage-sensing circuitry configured to detect a voltage level ofwelding power delivered from a power source to the welding tool,current-sensing circuitry configured to detect a current level of thewelding power, or a combination thereof.
 33. The system of claim 31,wherein the welding wire extends through the structural component. 34.The system of claim 31, wherein mechanical oscillation of the structuralcomponent has a substantially fixed travel distance.
 35. The system ofclaim 31, wherein mechanical oscillation of the structural component hasa substantially fixed frequency.
 36. The system of claim 31, wherein themechanical oscillation system comprises a motor and a mechanical linkageassembly coupled to the motor, wherein the mechanical linkage assemblyis fixedly attached to the structural component.
 37. The system of claim36, wherein the mechanical linkage assembly comprises a cam coupled tothe motor, and a piston coupled to the cam, wherein the piston isfixedly attached to the structural component.
 38. The system of claim31, wherein the welding tool comprises a liner extending into thestructural component, the welding wire extends through the liner, andthe structural component is directly coupled to the liner.